The present invention is directed to an apparatus and method for removing volatile organic compounds, such as petroleum hydrocarbons, from soil, as a means for the environmental clean up of a dump site, landfill or spill site.
Environmental laws have imposed requirements that remedial measures be taken in dump sites, landfills and following chemical spills, leakages or other accidents. This is particularly important in order to prevent chemicals from contaminating ground water due to percolation through the soil. When the chemical contaminant is a volatile organic compound, the remedial measures may involve removing such compounds from the soil by volatilization. Such volatilization can readily be accomplished by heating the soil in a furnace. However, this method requires that the soil be transported to a suitable processing facility for treatment. For all but very small clean ups, this method is prohibitively expensive in view of the high transportation costs required.
Consequently, it would be desirable to develop an apparatus and method for removing volatile organic compounds from contaminated soil while on-site, using as a means for such removal, equipment that is easily transported to that site. Since, with portable equipment, the volume of soil which can be processed at any one time will necessarily be limited, it would be desirable to provide a means for accelerating the volatilization rate so that the total clean up time is minimized.
Applicant's U.S. Pat. No. 5,052,858 disclosed an apparatus and method for removing volatile organic compounds from contaminated soil while on-site, using equipment that is easily transported to the site. According to that scheme, all of the hot gas used to strip the VOC from the soil was exhausted directly to atmosphere without cleanup. Although this approach affords an excellent response to environmental needs in many situations, it suffers from two drawbacks. First, the gas exhausted to atmosphere contains substantial heat which was added to the gas by burning a relatively expensive fuel--specifically, propane. Hence, the thermal efficiency and economy of the thermal stripping process is impaired. Second, since the stripping gas is laden with VOC, which are a source of air pollution, the amount of soil which can be treated per day is often limited by local environmental regulations.
Consequently, it would be desirable to provide a portable thermal stripping apparatus which minimizes the amount of supplemental fuel which must be burned to heat the stripping gas and which removes at least a portion of the VOC in the gas prior to exhausting it to atmosphere